A WCDMA communication terminal provided with a wireless LAN communication function is known in recent years. Such a mobile communication terminal is connected with a communication network such as internet through wireless communication with an access point for a wireless LAN, which is provided in places such as a station, an airport and a shopping center, to achieve data communication at relatively high speed. Users are generally satisfactory in many cases in terms of communication cost and communication speed more than communication services through WCDMA systems.
Meanwhile, a user of the mobile communication terminal is required to find out and go to a place where the access point for the wireless LAN is provided, and to start wireless LAN communication, if the user desires to receive benefits of such wireless LAN connection.
In order to allow automatic and prompt data communication through wireless LAN communication in an area where the wireless LAN communication is available, rather than starting the wireless LAN communication in response to an instruction from the user, the arrival of a so-called beacon signal transmitted from an access point for wireless LAN needs to be monitored constantly by the mobile communication terminal.
However, there is a problem of increased power consumption for constant monitoring. Therefore, it becomes important to efficiently monitor the arrival of a so-called beacon signal transmitted from the access point for wireless LAN.
By the way, as stated above, the access point for wireless LAN is often provided in places such as a station, an airport and a shopping center, or “indoors”. Furthermore, an area where communication with the access point for wireless LAN is possible is relatively narrow with a radius of several tens to 200 meters. Therefore, when moving at high speed, the mobile communication terminal has a low possibility of detecting the beacon signal transmitted from the access point for wireless LAN or tends to go beyond a communicable area of the access point soon even after detecting the beacon signal. In either case, it is difficult to receive wireless LAN service.
Considering the above two points, whether a wireless LAN connection is possible is divided into the following cases:
1) When the Mobile Communication Terminal is Stationary or Moving at a Low Speed:
It is highly probable to achieve the wireless LAN connection as long as the mobile communication terminal is present indoors. However, a probability of achieving the wireless LAN connection is low if the mobile communication terminal is present outdoors.
2) When the Mobile Communication Terminal is Moving at a High Speed:
There is a low probability of achieving the wireless LAN connection in both cases that the mobile communication terminal is present indoors and outdoors.
In this way, whether or not the wireless LAN connection can be achieved is dependent on conditions (i.e. position and speed) of the mobile communication terminals.
Japanese Patent Application Publication (JP-P2005-080071A) discloses a mobile communication terminal. The mobile communication terminal measures a position thereof by GPS (global positioning system) makes a determination to search an access point of for wireless LAN when the mobile communication terminal approaches the wireless LAN access point.
Japanese Patent Application Publication (JP-P2003-169011A) discloses a mobile communication terminal. At the time of waiting and receiving two kinds of signals with frequencies f1 and f2, the mobile communication terminal changes a period to receive the signal with the frequency f2 which differs from the signal with the predetermined frequency f1 in accordance with a moving speed of the mobile communication terminal.
Japanese Patent Application Publication (JP-P2003-309571A) discloses a wireless LAN system. According to this technique, a wireless terminal receives a beacon signal from an access points in a predetermined period.
Japanese Patent Application Publication (JP-P2003-318915A) discloses an information processing apparatus. The information processing apparatus determines whether it is present indoors or outdoors by a power source supplied from an AC adapter or a battery.
Japanese Patent Application Publication (JP-P2005-260987A) discloses a communication system. According to this conventional technique, a communication control section of a base station sets a period to transmit a beacon signal on the basis of a setting request received from a terminal station.
Japanese Patent Application Publication (JP-P2001-95063A) discloses a wireless receiver driven with a battery. The wireless receiver determines whether a transmission signal transmitted from a wireless transmitter non-periodically is present in accordance with a predetermined intermittent period. The wireless receiver changes the intermittent period in accordance with a usage state.
Japanese Patent Application Publication (JP-P2002-190769A) discloses a mobile communication apparatus. The mobile communication apparatus detects a reception level in order to determine whether or not the mobile communication apparatus is moving on the basis of variation history of the detected reception level.
There is also a paper “3GPP TS25.304 V5.3.0 (2003-06)” which discloses a technique to execute a switching process from a cell, where a mobile communication terminal receives services during moving at present to another cell by using data for HCS (hierarchical cell configuration).